The invention relates to new and useful improvements in electromotive actuators. More particularly, the invention relates to an electromotive actuator for a part which opens and closes (hereinafter termed a closing part), such as a window or a sliding roof in a motor vehicle.
German Utility Model 92 17 563 discloses an electromotive actuator for a closing part, for example for a motor vehicle window or a motor vehicle sliding roof, in which the position of the closing part is recorded electromotively and stored. When a specific distance from one end position of the closing part is reached, the motor power is reduced, whereby the speed of movement is reduced to a minimum value. This ensures a smooth and reliable run into the end position. Moreover, for protection against jamming, the power consumption of the electric motor is monitored against a previously stored power consumption.
European Patent 0,261,525 discloses a geared motor actuator for a motor vehicle window drive having a worm gear. The worm shaft is provided on an extended motor shaft end and drives a worm wheel. The worm wheel is axially plug-connected to an output driver plate by means of a fitting engagement. This driver plate drives the remaining window lifting mechanism. The worm gear arrangement uses the electric motor to drive the window pane with full torque into its end position, i.e., either the "window closed" or "window opened" position, until a limit stop is reached.
In order to dampen the impact stresses which otherwise would act on the motor and the other parts of the gear assembly, an elastic damping element is provided between the worm wheel and the driver plate mounted axially in front of the worm wheel. The worm wheel is driven by the motor shaft via the worm shaft and the driver plate is driven positively by means of the aforementioned plug connection. Consequently, when the window drive reaches one of the two end positions described above, the stop impact is reduced and absorbed radially and tangentially. It is also possible, instead of having a separate damping element, to design the components themselves to dampen impact stresses. This is done, for example, by placing elastic spokes along the transmission path between the worm shaft and the driver plate output.
German Laid-Open Publication 44 32 955 discloses an electromotive drive for a motor vehicle window. Its control device is provided with an excess force limitation function, such that the raising/lowering movement is terminated when the window reaches one of the two end positions provided with a corresponding limit stop. In addition, the excess force limitation is cut off automatically before the window reaches the upper seal. This prevents the increased drive forces which occur when the window enters the seal from triggering the excess force limitation. For this purpose, the window height corresponding to this distance is stored by assigning a fixed reference position to the window when it is in its closed position, with its top edge bearing on the upper limit stop. A position or movement counter can then sense from this reference position when the defined distance is reached as the pane moves upward. The excess force limitation can consequently be cut off automatically.